几乎没有什么流量的网站，Webmin/Virtualmin的apache日志里面也有MaxClients和ServerLimit错误，这是怎么回事？为什么Virtualmin/Webmin的apache的httpd日志总有MaxClients和ServerLimit错误？
tail -f /www.654z.com/log/httpd/error_log
WARNING: MaxClients of 256 exceeds ServerLimit value of 10 servers,
lowering MaxClients to 10. To increase, please see the ServerLimit
directive.
流量稍微大一点，就会有这个错误：
tail -f /www.654z.com/log/httpd/error_log
[error] server reached MaxClients setting, consider raising the MaxClients setting
神奇了，apache性能如此之差吗？不可能！ 肯定有原因。
经过仔细分析，httpd.conf 调用了 conf.d/*.conf 所有文件，会不会问题在这里？
[root@654z.com~]# grep ServerLimit /etc/httpd/conf.d/*
/etc/httpd/conf.d/swtune.conf:# ServerLimit: maximum value for MaxClients for the lifetime of the server
/etc/httpd/conf.d/swtune.conf:ServerLimit 10
果然，我们发现了 /etc/httpd/conf.d/swtune.conf 这个文件。
[root@www.654z.com ~]# more /etc/httpd/conf.d/swtune.conf
##
## Server-Pool Size Regulation (MPM specific)
##
# prefork MPM
# StartServers: number of server processes to start
# MinSpareServers: minimum number of server processes which are kept spare
# MaxSpareServers: maximum number of server processes which are kept spare
# ServerLimit: maximum value for MaxClients for the lifetime of the server
# MaxClients: maximum number of server processes allowed to start
# MaxRequestsPerChild: maximum number of requests a server process serves
<IfModule prefork.c>
StartServers 1
MinSpareServers 1
MaxSpareServers 5
ServerLimit 10 太XX了
MaxClients 10 太XX了
MaxRequestsPerChild 4000
</IfModule>
# worker MPM
# StartServers: initial number of server processes to start
# MaxClients: maximum number of simultaneous client connections
# MinSpareThreads: minimum number of worker threads which are kept spare
# MaxSpareThreads: maximum number of worker threads which are kept spare
# ThreadsPerChild: constant number of worker threads in each server process
# MaxRequestsPerChild: maximum number of requests a server process serves
<IfModule worker.c>
StartServers 1
MaxClients 10
MinSpareThreads 1
MaxSpareThreads 4
ThreadsPerChild 25
MaxRequestsPerChild 0
</IfModule>
真相大白，解决办法：
mv /etc/httpd/conf.d/swtune.conf /etc/httpd/conf.d/swtune.654z
然后重启apache，搞定！